$50 is too much. I got one for $30, and probably could of haggled down to $20. It's a buyer's market because all they can do is throw it out. No deposit or they'd of taken that, sits and takes up space, not exactly a large market for used kegs. Tell them if they won't take 20$ they can keep holding onto it, if they sell it, another will come along soon enough.
A good negotiating technique is to ask them how long they've had it so you know how much cleaning you're in for. It makes their imagination think how much crazy stuff could grow in there even though they really have no idea. Most people I've found that have them listed on CL will say oh it's been sitting in my garage for a year or 6 months either way both are easy enough to sell that it will require some good elbow grease to clean them up.
Last thing, always end with well good luck, if you don't get any buyers please let me know.
